Journal September 25, 2026 6 min read

What is Transepidermal Water Loss?

Transepidermal water loss (TEWL) is the passive diffusion of water through the stratum corneum. This page explains the measurement, its role in skin barrier research, and summarizes clinical and preclinical studies that

peptides-pro Editorial

What is transepidermal water loss?

Transepidermal water loss (TEWL) is the passive diffusion of water vapor from the dermis through the stratum corneum to the external environment. It is not sweat; it is insensible water movement driven by a concentration gradient. TEWL is measured in grams per square meter per hour (g/m²/h) using evaporimetry devices such as the Vapometer or Tewameter. In dermatological research, TEWL serves as a functional biomarker of skin barrier integrity: higher values indicate a more permeable barrier, while lower values suggest better barrier function. The concept is central to studies of xerosis, atopic dermatitis, and cosmetic efficacy.

The work described here centres on the stratum corneum barrier and its modulation by topical or oral agents, with TEWL as a primary outcome.

Research Studies

Vernix caseosa retention and atopic dermatitis prevention in newborns

Vernix caseosa is a naturally occurring, white, creamy substance that covers the skin of newborns at birth. A clinical trial is investigating whether retaining vernix caseosa after birth, rather than cleaning it off, can prevent atopic dermatitis (AD) in infants [1]. AD is a chronic inflammatory skin disease that often begins in infancy and affects up to one in five children worldwide. The trial focuses on primary prevention—stopping AD before it starts—by supporting skin-barrier integrity and the skin microbiome during early life [1]. TEWL is not listed as a primary outcome in the available summary, but the study addresses the same barrier biology that TEWL measures.

AP collagen peptides and skin hydration in a mouse model of oxazolone-induced atopic dermatitis

In a study using hairless mice with oxazolone-induced AD-like skin lesions, researchers evaluated AP collagen peptide (APCP), which contains collagen tripeptide (CTP), for effects on skin hydration and inflammatory responses [2]. The authors reported that APCP improved skin hydration and reduced transepidermal water loss in this animal model [2]. The work is preclinical; no human TEWL data are provided in the available summary.

Topical panthenol, niacinamide, and dipotassium glycyrrhizate in xerosis: a 28-day split-leg trial

A randomized, intra-individual, split-leg clinical trial tested a topical formulation containing panthenol, niacinamide, and dipotassium glycyrrhizate in subjects with xerosis cutis [3]. Participants applied the emollient twice daily for 28 days to one pretibial area, while the contralateral leg served as an untreated control. Assessments included TEWL and skin hydration. The study aimed to evaluate efficacy, tolerability, and subjective perception in dry, sensitive skin [3].

NPQ Plus supplementation and skin health in healthy adults

A single-arm, open-label study evaluated NPQ Plus, a multi-component nutraceutical containing polyphenols (Oligonol®), nicotinamide mononucleotide (NMN), pyrroloquinoline quinone (PQQ), coenzyme Q10, and a trace mineral complex, in 55 healthy adults with skin concerns [4]. Participants consumed one sachet daily for 12 weeks. Assessments at baseline and weeks 4, 8, and 12 included skin health parameters, antioxidant status, fatigue, and well-being [4]. TEWL is not specified among the outcomes in the available summary.

Emulgel with hyaluronic acid and sh-oligopeptide-1 in paediatric atopic dermatitis

A randomized, self-controlled trial in 57 children aged 2–14 with AD applied an emulgel containing hyaluronic acid, glycerol, grape seed oil, Calendula officinalis, aloe vera, and sh-oligopeptide-1 (a synthetic epidermal growth factor) twice daily for 10 days to one forearm, with the other forearm as control [5]. Skin barrier parameters including TEWL, stratum corneum hydration, erythema, and pH were measured. The study examined effectiveness for treating paediatric AD [5].

Oral bioactive collagen peptides and skin properties in women with facial wrinkles

A randomized, double-blind, parallel-group trial enrolled 68 healthy women aged 35–65 with visible facial wrinkles to assess whether daily oral collagen peptides improved age-associated skin parameters [6]. Participants received either an active control or avvera™ in a 1:1 ratio; 67 completed the study. TEWL is not listed among the outcomes in the available summary, but the trial addresses skin aging hallmarks that often include barrier function [6].

Vitamin K2 (MK-7) cream and skin hydration, elasticity, and wrinkles

A split-face/neck clinical trial is evaluating a facial and neck cream containing vitamin K2 (MK-7) in 36 women aged 35–60 with concerns of dryness, dullness, laxity, and neck lines [7]. The study measures skin hydration (Corneometer), transepidermal water loss (Vapometer), elasticity and firmness (Cutometer), and wrinkle severity (Rz and Ra via AEVA-HE imaging) compared to a control cream [7].

Mushroom extract topical formulation during breast radiotherapy

A study in women receiving radiotherapy to the breast after breast-conserving surgery randomly assigned participants to an investigational cosmetic formulation containing mushroom extract or usual moisturizing care [8]. The product was applied to intact breast skin twice daily starting about 15 days before radiotherapy, continuing through the ~3-week treatment period, and ending 1 month after radiotherapy. Skin condition was assessed before and during the study [8]. TEWL is not specified among the outcomes in the available summary.

Reference-only studies

Additional clinical investigations have used TEWL or related barrier measures as endpoints. A multicenter study evaluated temporally optimized antioxidant serums for daytime defense and nighttime repair in sensitive skin, linking oxidative stress and barrier dysfunction to skin biorhythms [9]. A randomized controlled trial assessed a comprehensive topical regimen incorporating niacinamide, Pro-Xylane, and panthenol after PicoWay laser for skin barrier repair and anti-aging effects [10]. A pilot study examined long-term effects of a hydrogel facial mask on hydration, barrier function, and mechanical properties in sensitive skin [11]. A real-world longitudinal study explored associations between a digital standardized skin care regimen and outcomes in acne-rosacea comorbidity, using cross-lagged and mediation analyses [12]. These reports support the broader context of TEWL as a research endpoint but are not the focus of this page.

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